Deep fat flyers, or gas fryers, are commercially used by restaurants, institutional kitchens, and fast food establishments for cooking a variety of food products, such as french fries, fish, fried chicken, and the like. The gas fryer must not only accommodate the individual heating requirements of each particular food product, but it must also maintain consistency and uniformity of taste and texture during the cooking process. The food product is cooked by totally immersing it within a vat or tank that is filled with heated oil or shortening. The oil is typically heated using a recirculating flow of heated gas that is forced or drawn through flow passages that are in thermal communication with wall portions of the cooking vat. In other prior art flyers, the flow passages are disposed within the vat itself in order to increase the heat transfer to the cooking oil. In both cases, however, maintaining a uniform temperature throughout the cooking zone of the shortening has proved a rather difficult manufacturing task. Examples of such prior art systems are shown in U.S. Pat. Nos. 4,481,873 to Keating; 4,848,317 to Prudhomme et al.; 4,898,151 to Luebke et al. and 5,050,582 to Almond et al.
Generally, in such prior art systems, the heated gas flows through the flow passages from an inlet to an outlet before being exhausted into the atmosphere. The heating systems of the prior art are extremely inefficient, however, and the average temperature of the exhaust gas is still extremely hot, on the order of 1200.degree. F. Due to the relatively short period of time in which the heated gas actually remains within the flow passages, the heat transfer to the cooking oil is thereby limited and potentially usable heating energy is wasted by being exhausted into the atmosphere.
Accordingly, in view of the foregoing, it is an object of the present invention to provide a gas fryer having a heating system which improves the overall efficiency of the fryer, reduces the exhaust temperature of the heated gas and which eliminates the problems and disadvantages found in the prior art.